In one mode of using a projector, a Personal Computer (PC) transmits screen data, which is displayed on the display of the PC, to a projector to project the screen data. Conventionally, a PC is in wired connection with a projector using a video signal line or a network cable. However, recently, a PC and a projector are wirelessly connected via a radio network.
In this case, however, there is a hardware limitation between the PC screen resolution and the projector projected screen resolution. Generally, the resolution of a PC is higher than that of a projector. Therefore, upon receiving screen data having a resolution which is higher than a resolution a projector specification, the projector may have to perform image processing (a reduction process). Further, although if the screen data are not frequently transmitted, the projector may have enough time to complete necessary image processing, if the screen data are transmitted more frequently, a processing load of the projector is increased. As a result, a phenomenon may occur that the image processing by the projector is delayed so that, for example, the images projected by the projector may become jumpy and not all the images transmitted from the PC can be projected (hereinafter the phenomenon is referred to as a “delay phenomenon”).
To resolve the problem, there is a known technique in which, when the screen delay between a PC and a projector is increased or when the projector cannot smoothly display the images, not all the screen data are transmitted by only the screen data of the part where a change is detected are transmitted (see, for example, Patent Document 1).